Translate all foo? -> is_foo. Close #334

The fancypants Hy award goes to Nick for coming up with the quoted
symbol hack for exports. This broke with foo?, since the export string
needs to be is_foo, but using a quoted string will pick up the change
due to it being a Symbol.

Mad clown love for that, @olasd.
Merge branch 'paultag/feature/support-question-marks' of https://github.com/paultag/hy into paultag-paultag/feature/support-question-marks

Conflicts:
	hy/core/language.hy